In a wireless communication system, a base station or other access node, referred to without limitation as a Node-B (NB), provides a coverage area in which the NB can serve user equipment devices (UEs), such as cell phones, tablet computers, machine-type-communication devices, tracking devices, embedded wireless modules, and/or other wirelessly-equipped communication devices (whether or not user operated). Further, the NB could be coupled with a core network that provides connectivity with various application servers and/or transport networks. With this arrangement, a UE within coverage of the NB could engage in air interface communication with the NB and could thereby communicate via the NB with various application servers and other entities.
Such a network could operate in accordance with a particular air interface protocol (or radio access technology), with communications from the NBs to UEs defining a downlink or forward link and communications from the UEs to the NBs defining an uplink or reverse link.
In accordance with the air interface protocol, each coverage area could operate on a carrier, which could be frequency division duplex (FDD), defining separate frequency channels for downlink and uplink communication, or time division duplex (TDD), with a single frequency channel multiplexed over time between downlink and uplink use. Further, on the downlink and uplink respectively, the air interface could be structured to define physical air interface resources for carrying information between the NB and UEs. For example, the air interface could be divided over time into frames, with each frame being divided in turn into subframes and timeslots, and the carrier bandwidth could be divided over frequency into subcarriers, which could be grouped within each timeslot to define physical resource blocks (PRBs) in which the subcarriers can be modulated to carry data.
Over the years, the industry has embraced various generations of air interface protocols, in a continuous effort to increase available data rate and quality of service for end users. These generations have ranged from “1G,” which used simple analog frequency modulation to facilitate basic voice-call service, to “4G”—such as Long Term Evolution (LTE), which now facilitates mobile broadband service using technologies such as orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO). And most recently, the industry is now exploring developments in “5G” and particularly “5G NR” (5G New Radio), which may use a scalable OFDM air interface, advanced channel coding, massive MIMO, beamforming, and/or other features, to support higher data rates and countless applications, such as mission-critical services, enhanced mobile broadband, and massive Internet of Things (IoT).